Can any element be a metal?

Question

I was reading that hydrogen can become a metal in some cases, like in Jupiter, and the same for helium. Is this true for all non-metals?

Answer 1

Assume you have a bunch of atoms consisting of some electrons in a bound state around a heavy core. If you increase the density($n$), you will eventually reach a point where the electrons Fermi energy($\sim n^{\frac{2}{3}}$) will be higher, then the binding energy of the outer electrons of your atoms, which will result in pressure ionization. You now have a system of positive ions, the kinetic energy of which depends on the temperature (their Fermi energy will be orders of magnitude lower then the electrons one because of their higher mass), and weakly interacting electrons, whose high kinetic energies will be independent of the temperature. If your temperature is sufficiently low, the positive ions will form a Coulomb crystal. You then have a solid containing electrons not bound in an atom, which is, what I would describe as metal. In my mind this could be realized independently of what element you are looking at.

So my answer is yes, any element should behave as a metal, if the density is high enough to produce degenerate electrons, but low enough, that the ions are non degenerate, and the temperature is low enough that the ions form a crystal.